/ Dictionary / Index L luminous flux: Meaning and Definition of Find definitions for: lu'minous flux' Pronunciation: [key] — Optics. Optics. the rate of transmission of luminous energy: expressed in lumens. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. luminous energy luminous flux density Related Content Daily Word Quiz: lunar Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language